Generally, a tennis court area is surrounded with a peripheral wall and a plurality of tennis courts are arranged therein just by drawing lines, and it is conventional that there is no partition wall serving as a boundary between one tennis court and another adjacent to it. It is also conventional that a wire-netting fence is provided at the portion rearward of the back line of each tennis court, and in which a sheet is stretched over the court side of the fence up to about 1 m above the ground, whereby a part of the wire-netting fence up to that height is covered with the sheet.
There is also another type of tennis court field constructed in such a manner that a concrete or wooden wall is built up rearward of the back line of each tennis court up to about 1 m above the ground, and a wire-netting fence is further installed on the wall.
When the wall located rearward of the back line of the tennis court is made of fully stretched sheet or hard material such as concrete as mentioned above, a tennis ball typically rebounds strongly without reduction of rebounding force after impact against the surface of the wall located rearward of the back line. If such a strong rebound of tennis ball takes place just at the rear of the back line, the ball may conveniently return back near to the player. However, if the ball is sent obliquely to either side of the wall rearward of the back line and runs into such a side, the ball will rebound toward the adjacent tennis court because there is no partition between the tennis courts adjacent to each other. As a result of this, the players on the adjacent court are obliged to interrupt the game to pick up the ball, and. Moreover the play going on in the adjacent court is also obliged to be interrupted when the tennis ball comes running in the adjacent court or service area thereof. If such an interruption occurs frequently, interest in the game itself may be lost. There is a further possibility that a player may accidentally tread on the tennis ball coming from the other court and fall down violently to be injured.
Hence, an object of the present invention is to provide a surface unit on a peripheral wall of a tennis court field having a plurality of tennis courts without partition between one court and the other, by which it is a tennis ball, moving obliquely over to either side of the surface of the wall rearward of the back line and impacting on it, has a reduced tendency to enter the adjacent court, and by which the tennis ball rebounds conveniently back to the original court where a game is going on.